Electrical outlet boxes have been molded from thermoplastic materials in recent years and there have been efforts to provide integral cable clamps on such boxes. The objective is to form a clamp adjacent an opening through a wall of the box such that an end of the cable can simply be pushed into the box through the opening and past the clamp whereupon the clamp will take effect, preventing extraction of the cable in the absence of some positive action to defeat the operation of the clamp. Examples of devices which have been developed for this purpose are found in U.S. Pat. Nos. 4,304,958, Neff et al; 4,366,343, Slater et al; 4,202,457, Tansi; and 4,304,957, Slater et al.
Boxes and clamp arrangements such as those shown in these patents have encountered problems and have generally not met the conflicting requirements of this industry. For example, an arrangement of the general type shown in the aforementioned Neff et al patent encounters the conflicting requirements presented by codes and standards governing structural and performance characteristics of electrical devices of this type, on the one hand, and the desires of the electricians who buy and use these devices, on the other. Specifically, the standards established by Underwriters Laboratories for a molded outlet box require that the flexible, movable portion of the clamp withstand a ten pound force in response to which it either must not move or, alternatively, it must return to its original position when the force is removed. Another U.L. requirement limits the size of the cable entrance opening as defined by the fixed regions surrounding the opening. Contrary to the force test requirement, electricians are interested in minimum resistance to cable insertion so as to permit quick and easy installation. It has been found to be quite difficult to produce a clamp having sufficient flexibility to be acceptable in the marketplace and also enough stiffness or resilience to return to its original position after the application of a ten pound force.